Thai boys a 'strong unit' says Beaconsfield survivor Todd Russell

As the rescue team embarks on the next stage of the operation to retrieve the boys still stranded in a flooded cave in Thailand, one Australian with intimate knowledge of their situation has spoken about how the boys and their coach could be feeling.

Todd Russell was along with Brant Webb one of the two survivors of the Beaconsfield mine collapse in 2006.

The pair were underground for six days before being found, and were trapped two weeks before a rescue could finally be carried out.

Todd Russell has said watching the ongoing rescue of the Thai boys has brought back many memories. (9news)

Tragically, a third miner, Larry Knight, was killed in the collapse.

Mr Russell said watching the ongoing rescue operation from Thailand had brought back "a lot of memories".

"It's something that's very close to my heart, obviously," he said.

The tortuous path of the cave provides a stern challenge to divers. (Supplied)

He said it had also been daunting for his family as the traumatic memories resurfaced.

"The idea of all these guys sticking together as one makes them a stronger unit."

Todd Russell and Brant Webb were freed after two weeks underground. ()

He praised the endurance and courage of the trapped boys and their coach, saying that he and Mr Webb had been "fortunate" in that they had been able to hear machinery operating, and know they were being searched for.

By contrast, he said, the Thai boys hadn't known "from one minute to the next" if help was on the way.

"For the families to be there waiting for their children to come out ... it must be hard at the moment," he said.

Rescuing the boys could take days. (9NEWS)

"Not knowing what boys are coming out, standing around waiting to see if it's their boys or somebody else's."

Four boys have so far been rescued from the cave complex.

Divers have since re-entered the labyrinthine tunnels to try to extract more of the stranded victims.